Re: [TCML] Questions on grounding

["Dex Dexter" <dexterlabs@xxxxxxxxxxx>]

Bart and everybody,

Bit off topic question.
I have heard of the possibility so called "overquenched gap".
How strong must be an airflow through the static gap of a NST coil to observe the effect of the "overquenching"?


Dex


--- bartb@xxxxxxxxxxxxxxxx wrote:

From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Cc:
Subject: Re: [TCML] Questions on grounding
Date: Tue, 21 Apr 2009 18:14:57 -0700

Hi Joe,

12" to 16" is good improvement.

Don't increase the spark gap. All this will do is increase the breakdown 
voltage and can kill the NST. A new gap would be good and the hyperbaric 
gap (linked the drawing in a post last week) is probably the easiest to 
build. It's basically a PVC T-fitting with copper pipes inserted into 
the ends along with a brass fitting on each end. The air is forced up 
through the center hole in the T-fitting. For your 12/30 NST, you can 
max out at about 27", so another 11" is about all you can expect out of 
the 12/30 on a perfect day. I think in order to achieve that or even 
come close, a new blown gap would be needed. That's up to you of course. 
If you do end up adding a 2nd 12/30 NST in parallel with the 1st NST, 
then you basically have a 12/60. Max length is about 38" with this 
setup. However, your cap would be very near NST resonance and it would 
be best to throw a little more capacitance into the gap if you think 
about doing that (about 0.018uF to .02uF is what you want with a 12/60).

The toroid may actually be too big, not too small. Install a breakout 
point (anything you come up with will do). I have a 1 meter aluminum 
ruler that I use for a breakout point and I simply lay it on top of the 
toroid when I use it. This will allow the spark to breakout more 
consistently and it helps direct the spark to one side of the coil. 
Actually when your testing spark lengths against a ground wire or 
object, try using a breakout point as it gives a precise measurement and 
you will get far more strikes to the object. The breakout point can be a 
wire, a ruler, a rod, and some even go as far as to attach a 1/2" to 1" 
metallic sphere to the end of the rod. The rod should protrude out past 
the toroid edge by about 5 to 10 inches on your toroid size.

I don't think you need to lower the toroid at all. If the bottom of the 
toroid is 2" above the secondary, then it should be fine where it is.

Take care,
Bart



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